Thermal hydrojet



Nov. 19, 1968 D. R. OLSEN THERMAL HYDROJET Filed July 15, 1966 lllll NN ON :llul'il N PE Douglas R. Olsen INVENTOR.

} BY Q0141 United States Patent 3,411,301 THERMAL HYDROJET Douglas R. Olsen, Richmond County, N.Y. (N. Quaker Hill Road, Pawling, N.Y. 12564) Filed July 15, 1966, Ser. No. 565,660 4 Claims. (Cl. 60221) ABSTRACT OF THE DISCLOSURE The invention is a marine propulsion system which increases the economy and thrust possible from a jet of hot combustion gases such as the discharge of a gas turbine. Water is inducted into a heat interchange chamber by the high velocity combustion gases. In the interchanger, a portion of the water is vaporized to steam, multiplying the velocity and thrust of the vapors leaving the interchanger. This is possible by the special designs of the water entry, venturi, and heat interchanger sections. The thermal hydrojet may be mounted beneath the hull of a vessel making it especially useful for hydrofoil craft.

This invention comprises a novel and useful propulsion engine for watercraft, and more particularly to a thermal hydrojet comprised of a thermal turbine, hydrotube, and a heat interchanger.

A main object of the invention is to provide an efficient propulsion system for high speed watercraft.

A further object of the invention is to provide a propulsion system that does not require the use of geared power transmission systems.

A further object of the invention is to provide a propulsion system that does not have rotating parts in contact with water.

Further objects and advantages will become apparant from the following descriptions and claims, and from the accompanying drawing wherein: I

FIGURE 1 is an elevation in section of the thermal hydrojet attached to the hull of a watercraft.

FIGURE 2 is an enlarged section of the heat interchanger rods, illustrating the passage of water, steam, and exhaust gasses over said rods.

In W. R. Christensen, US. Patent 2,948,739 a water jet propulsion system is described. In that system a gas turbine drives an air compressor and a water pump. The water pump by various means induces a flow of cold water into an underwater chamber wherein said water is further mixed with cold air from the air compressor and exits from the chamber as a high speed jet of water and air which propels the watercraft and reduces the friction drag of the water on the hull. The exhaust from the turbine is conducted to the atmosphere and further aids the propulsion. In that device a high speed :pump is necessary, and the main effect of the discharge of air under water is to reduce friction drag. The pump is subject to serious danger from foreign objects in the water, as well as erosion due to cavitation at the high speeds at which it operates.

In Jerry B. Campbell, US. Patent 3,153,905 a jet engine is described that obtains propulsion by burning a combustible mixture in an underwater combustion chamber, exhausting the products of combustion radially to the combustion chamber, which is rotatable. The thrust developed rotates the combustion chamber and its attached propeller blades which propel water through a tube and thereby propel the vessel. Some benefit is obtained .by the exhaust gasses, but very little since they are practically spent in rotating the propeller blades and combustion chamber. -No method is taught of how to supply the necessary pressure to deliver the combustion mixture to the combustion chamber, this being an im- 3,411,301 Patented Nov. 19, 1968 "ice portant step to the successful operation of the engine. The device also suffers from the problems of cavitation inherent in rotating machinery in water at high speed.

By my invention the advantages of water jet propulsion for high speed watercraft can be obtained efficiently without subjecting machinery to high speed rotation in contact with water with the consequential erosion and cavitation. Further, the novel arrangements of elements enables jet propulsion with an extraordinary thermal efficiency.

Referring to the drawing:

FIGURE 1 shows a thermal hydrojet 4, mounted beneath watercraft 1 by a combination keel and support 2, and located well below the surface of the water 3. Water is free to enter the hydrotube 4, at 5, and pass through the annulus between the gas turbine 7, and the inner walls of the tube and flow out through the venturi 8, diverging cone 9, over the heat interchanger 10, and discharge at nozzle 6.

In operation, the gas turbine 7, is started by the starting motor 19, which is also wired as a generator to recharge batteries when the turbine is running. Air is drawn into the air supply pipe 11, and enters the air compressor 13. Air is compressed to pressures in the range of six to twenty atmospheres. Fuel is injected and ignited and the air and fuel burn in combustion chamber 14, and discharge to the turbine wheel 16. The methods for compressing the air and burning the fuel are well known in the art. The tunbine wheel is rotated by the hot gasses which enter at temperatures of 1200 to 1800 degrees Fahrenheit and pressures of six to twenty atmospheres. The rotation of the turbine wheel drives the air compressor which is mounted on the common shaft 15.

The power extracted by the turbine wheel causes a drop in the temperature and pressure of the gases. The amount of power extracted is the sum of the power necessary to drive the air compressor, overcome friction, and to generate auxiliary electric power for charging batteries, operating lights, and similar auxiliary devices on the watercraft. This auxiliary electric power however is a very small fraction of the total power available. However, the discharge temperature will vary according to turbine design, and the amount of auxiliary power extracted, but will not be lower than 700 degrees Fahrenheit, and will usually be higher.

The hot exhaust gases are conducted through the convergent nozzle 17 and discharged in a jet toward the venturi 8 at high velocity. The very high velocity and venturi construction causes a low pressure area at 18 thereby inducing water to be entrained in the jet and be drawn into inlet 5. The flow of water is increased as the craft is propelled at higher velocities. This flow of water around the turbine is also beneficial in cooling the walls of the combustion chamber and thereby improving their life.

After passing through the venturi, the exhaust gas with entrained water enters the heat interohanger consisting of divergent tube section 9, and the heat interchanger rods 10. In this section a portion of the entrained water is vaporized to steam while the exhaust gases are some- What cooled. The net result of the steam formation and gas cooling is a marked net increase of the exhaust mixture and therefore a marked increase in the propulsive force when discharged as a jet from nozzle 6.

For a typical exhaust gas at degrees Fahrenheit having as an average a heat capacity of 8.25 B.t.u./ pound mole per degree Fahrenheit and cooling to 300 degrees in the heat interchanger, there is a heat of 57,500 Btu. released per pound mole to heat and vaporize water. There is a reduction in the volume of the gas from 1070 cubic feet to 570 cubic feet. The heat released is capable of heating 54 pounds of water from 60 degrees Fahrenheit to steam at 212 degrees Fahrenheit. The change in volume of the water is 1450 cubic feet. Therefore the net change of the volume of the mixture is an increase of 380 cubic feet. The resultant volume is therefore approximately 126% of the original, giving the entire mass a greater discharge velocity. Since both the mass and the discharge velocity are higher than that which could be obtained from the conventional discharge of the hot jet alone, thethrust and therefore the efliciency and economy is improved. Further, the cooler underwater exhaust also results in less of a safety hazard and also in the reduction of the engine noise level.

FIGURE 2 shows the operation of the heat interchanger tubes which are located in the divergent tube 9. Several interchanger tubes are shown with their novel construction. Each rod has a semicircular cross section 21, facing downstream, and a triangular cross section facing upstream, 2t), terminated by a leading edge 22.

Hot exhaust gasses with relatively large water drops entrained flow at high velocity from the venturi 8, toward the rods. Some of the drops impinge upon the leading edge of a rod, breaking into a film that flows across the surface of the rod. Heat is efficiently transferred to the rod by the high velocity hot gasses and thence to the water film. Also the slowing of the water in relation to the exhaust gas increases the heat transfer, which is also aided by the increase in surface of the water presented to the gas. Any water flowing off the downstream side of the rods will be in smaller drops than those that impinged upon the rods. Succeeding rows of these rods are added to achieve the desired heat transfer. The heat interchanger has the advantages of high efliciency, with a very low pressure drop. It also has the advantage in that it can be ruggedly constructed to stand the highly erosive conditions that will prevail. While the thermal hydrojet will continue to perform without the interchanger rod, the rods substantially improve the efiiciency.

While a specific embodiment of a thermal hydrojet have been disclosed in the foregoing description, it is understood that variou modifications within the spirit of the invention may occur to those skilled in the art. Therefore, it is intended that no limitations be placed upon the invention except as defined by the scope of the appended claims.

What is claimed is:

1. A marine propulsion engine consisting of a tube having open ends and a varying cross section internally such that water may enter at the front, flow around the exhaust nozzle of a high temperature combustion products generator, said tube forming a venturi rearwardly of the gas exhaust nozzle, at which venturi, said gas exhaust nozzle may direct the products of combustion, and after said venturi the cross section of the tube increases in a heat interchange section, means in said heat interchange section for increasing energy exchange between said combustion products and said water, said interchange section discharging to the surrounding water, wherein the propulsion engine may develop a thrust by the discharge of hot exhaust gas into the venturi throat thereby entraining water and forming steam, and discharging the mixture of steam, water and gas rearwardly at relatively high velocity.

2. The combination of claim 1 wherein a gas turbine is mounted axially inside said tube, where the gas turbine has air and fuel supply pipes from the watercraft to which the engine is attached, and said turbine being provided with an air compressor, a combustion chamber, and a turbine driven by the products of combustion, said turbine driving the air compressor, and thence the products of combustion discharged from the turbine are directed to the venturi of the aforesaid tube in the form of a jet which entrains the neighboring water.

3. A marine propulsion engine consisting of a tube supported from a watercraft and being open to the water at both ends and having a gas turbine mounted axially within said tube in such a manner as to provide a water passage between the walls of the tube and the outer shell of the gas turbine, said turbine having an air supply pipe and a fuel supply pipe extending through the tube to the watercraft, and said turbine consisting of a combustion chamber, air compressor, turbine and exhaust gas discharge nozzle, said discharge nozzle arranged to discharge in the direction of the venturi formed by a reduction in the internal cross section of the aforesaid tube, and attached to said tube, a heat interchanger section shaped as a cone which expands from the aforesaid venturi and is transversed by rows of rods, wherein each of the rods has a semicircular cross section facing downstream and a triangular cross-section facing upstream, whence the exhaust gas mixture discharges to the surrounding water.

4. A marine propulsion engine consisting of a tube having open ends and a varying cross-section internally such that water may enter at the front, flow around the exhaust nozzle of a high temperature gas exhaust nozzle, said tube forming a venturi rearwardly of the gas exhaust nozzle, at which venturi said gas exhaust nozzle may direct the products of combustion, and after said venturi, the cross-section of the tube increases in a heat interchange section, said interchange section including rows of transverse heat interchange rods having a cross-section that presents a sharp triangular surface to the mixture flowing out of the venturi and a blunt or semi-circular surface facing the discharge of the tube, said interchange section discharging to the surrounding water, wherein the propulsion engine may develop a thrust by the discharge of hot exhaust gas into the venturi throat, thereby entraining water and forming steam, and wherein more steam is formed on the rods of the interchanger and discharging the mixture of steam, water, and gas rearwardiy at relatively high velocity.

References Cited UNITED STATES PATENTS 2,528,354- 10/ 1950 Flanagan -h 6 0-221 2,543,024 2/ 1951 Humphrey 60-221 3,232,047 2/1966 Wille 60--221 MARTIN P. SCHWADRON, Primary Examiner.

D. HART, Assistant Examiner. 

